Reactions of Secondary Allylamines with Bis(η⁵:η¹-pentafulvene)titanium Complexes: Selective Formation of Monoazabutadiene Titanium Complexes by N–H and C–H Bond Activation

Abstract

The N−H and C−H bond activation reactions at ambient conditions of seven different secondary allyl amines (Aa−g) with bis(η 5 :η 1 -pentafulvene)titanium complexes (1) h a v e b e e n i n v e s t i g a t e d . B i s ( η 5 : η 1adamantylidenepentafulvene)titanium (1a) reacts with Nallylaniline (Aa), N-allylbenzylamine (Ac), N-allyl-tert-butylamine (Ad), N-allylcyclohexylamine (Ae), and N-allyl-2methylaniline (Af) to give the 1-azabutadiene complexes 2a,c−f with high yields. They are the first complexes of the CH 2 -terminated monoazadiene RNCHCHCH 2 . Using bis(η 5 :η 1 -di-p-tolylpentafulvene)titanium (1b), which exhibits a less Brønsted basic C exo center, and Aa, the β-C−H bond activation can be slowed down so much that the agostic interaction between the titanium center and the C−H bond is detectable via NMR measurements at room temperature. In the reactions of the titanium azabutadiene complexes 2a,b and 3a with carbon monoxide a ligand exchange is observed, forming the titanocene dicarbonyls 4a,b.

From Five to Seven: Ring Expansion of Monoazadiene Titanium Complexes by Insertion of Aldehydes, Ketones and Nitriles

“…The 15 N HMBC spectra of compounds 3 a – 3 e reveal one signal each for the nitrogen atoms with shifts between 186 and 201 ppm. These signals are shifted approximately 50 ppm to higher fields in comparison to the monoazabutadiene titanium complexes 2 a ( 15 N , δ =249 ppm) and 2 b ( 15 N , δ =248 ppm) …”

“…The bis( η 5 , η 1 ‐pentafulvene)titanium 1 a and 1 b were synthesized according to known procedures, as well as the titanium monoazabutadiene complexes 2 a and 2 b …”

“…Recently, we reported a new and efficient synthetic route to titanium monoazabutadiene complexes 2 via N−H and C−H bond activation of secondary allylamines with bis( η 5 : η 1 ‐pentafulvene)titanium complexes 1 at ambient temperatures in high yields (Scheme ) …”

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

“…The η 5 : η 1 ‐pentafulvene complexes of titanium with secondary allylamines again with simultaneous N−H and C−H bond activations, however, in this case formation of titanocene 1‐azabutadiene complexes occurs (Scheme ) …”

“…[39] The η 5 : η 1 -pentafulvene complexes of titanium with secondary allylamines again with simultaneous NÀ H and CÀ H bond activations, however, in this case formation of titanocene 1azabutadiene complexes occurs (Scheme 8). [52] The main features of these reactions is the possibility to slelectively obtain in the first step the η 5 -Cp' ligands substituted metallocene complexes by conversion of η 5 : η 1 -pentafulvene ligands which in a second step yield synthetically very interesting metallacycles. Aditionally, by other reactions the 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 conversion of only one pentafulvene [C 5 H 4 =CR 2 ] 2À to Cp' ligands [C 5 H 4 À CHR 2 ] 1À was described whereas the other remains as [C 5 H 4 =CR 2 ] 2À ligand.…”